1. Field of the Invention
The present invention relates to a liquid crystal display device.
2. Discussion of the Related Art
Until recently, display devices have typically used cathode-ray tubes (CRTs). Presently, many efforts and studies are being made to develop various types of flat panel displays, such as liquid crystal display (LCD) devices, plasma display panels (PDPs), field emission displays, and electro-luminescence displays (ELDs), as a substitute for CRTs. Of these flat panel displays, LCD devices have many advantages, such as high resolution, light weight, thin profile, compact size, and low voltage power supply requirements.
In general, an LCD device includes two substrates that are spaced apart and face each other with a liquid crystal material interposed between the two substrates. The two substrates include electrodes that face each other such that a voltage applied between the electrodes induces an electric field across the liquid crystal material. Alignment of the liquid crystal molecules in the liquid crystal material changes in accordance with the intensity of the induced electric field into the direction of the induced electric field, thereby changing the light transmissivity of the LCD device. Thus, the LCD device displays images by varying the intensity of the induced electric field.
The LCD device requires a backlight unit to supply light to a liquid crystal panel. The backlight unit is categorized into a direct type and an edge type. The edge type backlight unit has a configuration that a light source is arranged at one or more side of a light guide plate while the direct type backlight unit has a configuration that a light source is arranged below a liquid crystal panel.
The edge type backlight unit has an advantage of thin profile compared to the direct type. Recently, light emitting diodes (LEDs) are widely used as light sources of a backlight unit because the LEDs have advantages of small size, low power consumption, and high reliability.
FIG. 1 is a cross-sectional view illustrating an LCD device including an edge type backlight unit using an LED according to the related art, and FIG. 2 is a schematic plan view illustrating the LCD device according to the related art.
Referring to FIG. 1, the LCD device includes a liquid crystal panel 10, a backlight unit 20, a main supporter 30, a bottom case 50, and a top case 40.
The liquid crystal panel 10 includes first and second substrates 12 and 14, and a liquid crystal layer therebetween. Polarizing plates are attached on a top surface of the second substrate 14 and a bottom surface of the first substrate 12.
The backlight unit 20 is below the liquid crystal panel 10. The backlight unit 20 includes a light guide plate 23, an LED package 29 along a side of the light guide plate 23, a reflecting sheet 25 below the light guide plate 23, and at least one optical sheet 21.
The liquid crystal panel 10 and the backlight unit 20 are assembled along with the main supporter 30 surrounding sides thereof, the top case 40 covering top peripheral portions of the liquid crystal panel 10, and the bottom case 30 covering a bottom of the backlight unit 20.
The LED package 29 includes a LED printed circuit board (PCB) 29b, and a plurality of LED chips 29a mounted on the LED PCB 29b along a length direction of the LED PCB 29b. 
The LED package 29 is fixed in position through a adhesive and the like so that lights emitted from the LED chips 29a are incident on a light entering surface of the light guide plate 23.
Accordingly, the light from the LED chip 29a is incident on the light entering surface, then is refracted in the light guide plate 23 and goes out upward, then passes through the optical sheet 21 along with a light reflected by the reflecting sheet 25 and is thus converted into a high-quality plane light, and then is supplied to the liquid crystal panel 10.
In the above-described LCD device, the LED PCB 29b is located only at a side where a driving circuit is located, as shown in FIG. 2. This configuration does not meet the needs of high brightness, 400 nit or more.
Further, the LED package 29 requires a predetermined light diffusion distance. Accordingly, in the case of less than the predetermined light diffusion distance, hot spots that bright and dart portions alternate occurs in a display region at a side where the LED backlight unit is located.